Method of manufacturing a MOSFET on an SOI substrate

ABSTRACT

Occurrence of short-channel characteristics and parasitic capacitance of a MOSFET on a SOI substrate is prevented. 
     A sidewall having a stacked structure obtained by sequentially stacking a silicon oxide film and a nitride film is formed on a side wall of a gate electrode on the SOI substrate. Subsequently, after an epitaxial layer is formed beside the gate electrode, and then, the nitride film is removed. Then, an impurity is implanted into an upper surface of the semiconductor substrate with using the gate electrode and the epitaxial layer as a mask, so that a halo region is formed in only a region of the upper surface of the semiconductor substrate which is right below a vicinity of both ends of the gate electrode.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese Patent ApplicationNo. 2012-011213 filed on Jan. 23, 2012, and Japanese Patent ApplicationNo. 2012-163907 filed on Jul. 24, 2012, the content of which is herebyincorporate-′ by reference into this application.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a semiconductor device and a method ofmanufacturing the same. More particularly, the present invention relatesto a technique effectively applied to a semiconductor device using a SOI(Silicon On Insulator) substrate and to a method of manufacturing thesame.

BACKGROUND OF THE INVENTION

As a semiconductor device capable of suppressing generation of parasiticcapacitance, a semiconductor device using a SOI substrate is currentlyused. The SOI substrate is a substrate obtained by forming a BOX (BuriedOxide) film (embedded oxide film) on a supporting substrate made ofhigh-resistance Si (silicon) or others and forming a thin layer (siliconlayer) mainly containing Si (silicon) on the BOX film. When a MOSFET(Metal Oxide Semiconductor Field Effect Transistor: MOS field-effecttransistor) is formed on the SOI substrate, the parasitic capacitancegenerated in a diffusion region formed in the silicon layer can bereduced. Therefore, by manufacturing a semiconductor device by using theSOI substrate, improvement in an integration density and an operatingspeed of the semiconductor device, achievement of latch-up free, etc.can be expected.

Patent Document 1 (Japanese Patent Application Laid-Open Publication No.2009-158677) describes a technique that a nitride film for a dummysidewall is formed on a side wall of a gate electrode on a SOI substratevia an oxide film for a sidewall, and then, a selective epitaxial growthregion is formed on a SOI layer of an upper surface of the SOIsubstrate, followed by removal of the nitride film for the dummysidewall, and then, implantation of an impurity for extension and animpurity for halo into the supporting substrate. Here, the document doesnot specifically describe at which position in the supporting substratea Halo portion (halo region) formed in the supporting substrate isformed, and does not describe how different a concentration of theimpurity configuring the Halo portion is between a portion right belowthe gate electrode and other regions, either.

Patent Document 2 (Japanese Patent Application Laid-Open Publication No.2007-188992) describes a technique that, when a MOSFET is formed on theSOI substrate, a high-concentration diffusion region is formed in avicinity of a surface of the supporting substrate right below the gateelectrode, the high-concentration diffusion region being formed inregions which are below a drain region and below a source region and ata predetermined depth from the surface of the supporting substrate.

Patent Document 3 (Japanese Patent Application Laid-Open Publication No.2010-251344) describes a technique that a p-well is formed in the entireupper surface of a silicon substrate below the SOI substrate, and ann-channel-type MIS transistor is formed on the SOI layer thereon.

SUMMARY OF THE INVENTION

When a MOSFET is provided on a SOI substrate, there is an advantage thatminiaturization of the MOSFET is facilitated. However, if the MOSFET isminiaturized, short-channel characteristics (short-channel effect) aredeteriorated, and there is a problem that the performance of thesemiconductor device is lowered.

Also, in order to suppress the short-channel characteristics, it isconceivable to form a halo region, which is a high-concentrationdiffusion region, in a supporting substrate. However, when the haloregion is formed in the upper surface of the supporting substrate whichis right below the gate electrode, there is a problem that the effect ofsuppressing the short-channel characteristics cannot be obtained well.

Further, when the halo region is formed in the entire upper surface ofthe supporting substrate, the halo region exists right below thehigh-concentration diffusion region which configures the source/drainregions, and therefore, there is a problem that diffusion capacitance isgenerated between the source/drain regions and the halo region via theBOX film.

Other preferred aims and novel characteristics will be apparent from thedescription of the present specification and the accompanying drawings.

The typical ones of embodiments disclosed in the present applicationwill be briefly described as follows.

In a method of manufacturing a semiconductor device according to oneembodiment, a sidewall is formed on a side wall of a gate electrode on aSOI substrate, and then, an epitaxial layer is formed on a silicon layeron an upper surface of the SOI substrate, followed by removal of thesidewall, and then, implantation of an impurity with using the gateelectrode and the epitaxial layer as a mask, so that a halo region isformed in an upper surface of a supporting substrate.

According to one embodiment disclosed in the present application,performance of a semiconductor device can be improved. Moreparticularly, short-channel characteristics of the semiconductor devicecan be suppressed.

Also, generation of diffusion capacitance can be suppressed.

BRIEF DESCRIPTIONS OF THE DRAWINGS

FIG. 1 is a cross-sectional view illustrating a method of manufacturinga semiconductor device according to a first embodiment of the presentinvention;

FIG. 2 is a cross-sectional view illustrating the method ofmanufacturing the semiconductor device continued from FIG. 1;

FIG. 3 is a cross-sectional view illustrating the method ofmanufacturing the semiconductor device continued from FIG. 2;

FIG. 4 is a cross-sectional view illustrating the method ofmanufacturing the semiconductor device continued from FIG. 3;

FIG. 5 is a cross-sectional view illustrating the method ofmanufacturing the semiconductor device continued from FIG. 4;

FIG. 6 is a cross-sectional view illustrating the method ofmanufacturing the semiconductor device continued from FIG. 5;

FIG. 7 is a cross-sectional view illustrating the method ofmanufacturing the semiconductor device continued from FIG. 6;

FIG. 8 is a cross-sectional view illustrating a method of manufacturinga semiconductor device according to a second embodiment of the presentinvention;

FIG. 9 is a cross-sectional view illustrating the method ofmanufacturing the semiconductor device continued from FIG. 8;

FIG. 10 is a cross-sectional view illustrating the method ofmanufacturing the semiconductor device continued from FIG. 9;

FIG. 11 is a cross-sectional view illustrating the method ofmanufacturing the semiconductor device continued from FIG. 10;

FIG. 12 is a cross-sectional view illustrating the method ofmanufacturing the semiconductor device continued from FIG. 11;

FIG. 13 is a cross-sectional view illustrating a method of manufacturinga semiconductor device according to a third embodiment of the presentinvention;

FIG. 14 is a cross-sectional view illustrating the method ofmanufacturing the semiconductor device continued from FIG. 13;

FIG. 15 is a cross-sectional view illustrating the method ofmanufacturing the semiconductor device continued from FIG. 14;

FIG. 16 is a cross-sectional view illustrating the method ofmanufacturing the semiconductor device continued from FIG. 15;

FIG. 17 is a cross-sectional view illustrating the method ofmanufacturing the semiconductor device continued from FIG. 16;

FIG. 18 is a cross-sectional view illustrating a method of manufacturinga semiconductor device as a comparative example;

FIG. 19 is a cross-sectional view illustrating a method of manufacturinga semiconductor device as another comparative example; and

FIG. 20 is a cross-sectional view illustrating a semiconductor device asa comparative example.

DESCRIPTIONS OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments will be described in detail with reference tothe drawings. Note that members having the same function are denoted bythe same reference symbols throughout all drawings for describing theembodiments, and the repetitive description thereof will be omitted.Also, in the following embodiments, the description of the same orsimilar parts will not be repeated unless particularly required.

First Embodiment

Manufacturing steps of a MOS-type field-effect transistor (hereinafter,simply referred to as “MOSFET”) according to the present embodiment willbe explained with reference to drawings. FIGS. 1 to 7 arecross-sectional views during the manufacturing steps of a semiconductordevice according to the present embodiment such as a semiconductordevice having an n-channel-type MOSFET on a SOI substrate.

First, as illustrated in FIG. 1, a semiconductor substrate 1 including aBOX film 2 and a silicon layer (SOI layer) 3 stacked in an upper portionthereof is prepared. The semiconductor substrate 1 is a supportingsubstrate made of Si (silicon), the BOX film 2 on the semiconductorsubstrate 1 is a silicon oxide film, and the silicon layer 3 on the BOXfilm 2 is a layer made of monocrystalline silicon having a resistance ofabout 1 to 10 Ωcm.

The SOI substrate formed of the BOX film 2 and the silicon layer 3 canbe formed by a SIMOX (Silicon Implanted Oxide) method in which O₂(oxygen) is ion-planted at high energy into a principal surface of thesemiconductor substrate 1 made of Si (silicon) and the Si (silicon) isbound with the oxygen in a subsequent thermal treatment to form a buriedoxide film (BOX film) at a position slightly deeper than the surface ofthe semiconductor substrate. Alternatively, the SOI substrate can beformed by adhering the semiconductor substrate 1 including an oxide filmformed on a surface thereof to another semiconductor substrate made ofSi (silicon) by applying high heat and a pressure thereto, and then,thinning a silicon layer on one side thereof by polishing.

Next, as illustrated in FIG. 2, a p-type impurity (for example, B(boron)) is implanted into the silicon layer 3 at a relatively lowconcentration by an ion implantation method, and then, a silicon oxidefilm (an insulating film for a gate insulating film 4) is formed on thesilicon layer 3 by using a thermal oxidation method, a CVD (ChemicalVapor Deposition) method, or others. Then, a polysilicon film (aconductor film for a gate electrode 5) and a silicon nitride (Si₃N₄)film 6 are sequentially formed on the silicon oxide film by using theCVD method or others, and the silicon nitride film 6 is patterned byusing a photolithography technique and a dry etching method.Subsequently, the polysilicon film and the silicon oxide film arepatterned by the dry etching method with using the silicon nitride film6 as a hard mask. In this manner, the gate insulating film 4 formed ofthe silicon oxide film is formed on the silicon layer 3, and the gateelectrode 5 formed of the polysilicon film is formed on the gateinsulating film 4.

Note that the polysilicon film configuring the gate electrode 5 is setto be a low-resistance n-type semiconductor film (doped polysiliconfilm) obtained by ion-implanting an n-type impurity such as P(phosphorous) or As (arsenic) thereto. Also, the polysilicon film whichis an amorphous silicon film upon film formation can be changed into apolycrystalline silicon film by thermal treatment after the filmformation (after the ion implantation).

Subsequently, a silicon oxide film 7 and a silicon nitride (Si₃N₄) film8 a are formed by using, for example, the CVD method so as to cover theupper surface of the silicon layer 3 and the gate electrode 5, and then,the silicon oxide film 7 and the silicon nitride film 8 a are partiallyremoved by performing anisotropic etching by a RIE (Reactive IonEtching) method or others to expose the upper surface of the siliconlayer 3. In this manner, a stacked film formed of the silicon oxide film7 and the silicon nitride film 8 a is formed on the side wall of thegate electrode 5 in self alignment.

Here, the silicon oxide film 7 is an insulating film for forming a sidewall, and the silicon nitride film 8 a is an insulating film for forminga dummy side wall for forming an epitaxial layer (elevated layer,selective growth layer) at a position away from the gate electrode in alater step. That is, the stacked film formed of the silicon oxide film 7and the silicon nitride film 8 a is the dummy side wall, and the siliconoxide film 7 remains but the silicon nitride film 8 a does not remain ina completed semiconductor device.

Then, as illustrated in FIG. 2, an epitaxial layer 9 mainly made of Si(silicon) is formed on the upper surface of the silicon layer 3, whichis exposed from the gate electrode 5, the silicon oxide film 7, and thesilicon nitride film 8 a, by using the epitaxial growth method. In thismanner, a silicon layer whose upper surface is higher than the siliconlayer 3 is formed in a region outside the gate electrode 5, the siliconoxide film 7, and the silicon nitride film 8 a.

At this time, the upper surface of the epitaxial layer 9 is not alongthe side wall of the gate electrode 5 but along the upper surface of thesilicon layer 3, and is at a position higher than an upper surface ofthe formed silicon oxide film 7 in a film thickness. That is, while thefilm thickness of the silicon oxide film 7 is about 5 nm, the epitaxiallayer 9 has a film thickness of 20 to 50 nm which is thicker than a filmthickness of the silicon oxide film 7.

Note that the formation of the epitaxial layer 9 beside the gateelectrode 5 results from an extremely-thin film thickness of the siliconlayer 3. And, the is because, when a silicide layer is formed onsurfaces of the source/drain regions configuring a MOSFET in a laterstep, if the source/drain regions are formed in the silicon layer 3without forming the epitaxial layer 9, the silicon for forming thesilicide layer is not sufficient only from the film thickness of thesilicon layer 3. That is, one of reasons for forming the epitaxial layer9 is that it is required to compensate for the film thickness of thesilicon layer which configures the source/drain regions when thesilicide layer and the source/drain regions are formed. Further, anotherreason for forming the epitaxial layer 9 is cited as prevention ofincrease in the parasitic resistance accompanied by the source/drainregions of the MOSFET.

Next, as illustrated in FIG. 3, the silicon nitride film 6 above thegate electrode 5 and the silicon nitride film 8 a which is theinsulating film for forming the dummy side wall are removed by using awet etching method.

Then, as illustrated in FIG. 4, an n-type impurity (for example, As(arsenic)) is implanted into the upper surface of the silicon layer 3 ata relatively low concentration by using the ion implantation method withusing the gate electrode 5 as a mask, so that an extension region 10 isformed in an upper surface of the epitaxial layer 9 and an upper surfaceof the silicon layer 3 which are exposed from sides of the gateelectrode 5 and the gate insulating film 4. The extension region 10 isnot formed in at least a part of the upper surface of the silicon layer3 right below the gate electrode 5. Also, the impurity ions implanted inthis ion implantation step transmit through the silicon oxide film 7having a film thickness of about 5 nm, and therefore, the extensionregion 10 is formed also in the silicon layer 3 right below the siliconoxide film 7.

Note that the extension region 10 is illustrated in the vicinity of theupper surface of the silicon layer 3 in FIG. 4. However, the extensionregion 10 may be formed from the upper surface of the silicon layer 3 toa lower surface thereof.

Next, as illustrated in FIG. 5, a p-type impurity (for example, B(boron)) is implanted into the upper surface of the semiconductorsubstrate 1 from above the semiconductor substrate 1 at a relativelyhigh concentration by using the ion implantation method with using thegate electrode 5 and the epitaxial layer 9 as a mask, so that a haloregion (p-type semiconductor region) 11 is formed right below a portionbetween the gate electrode 5 and the epitaxial layer 9 in the uppersurface of the semiconductor substrate 1. The halo region 11 is asemiconductor region (diffusion layer) formed for suppressing theshort-channel characteristics of the MOSFET formed in a later step.

Here, the p-type impurity (for example, B (boron)) is almost notintroduced into the semiconductor substrate 1 right below the gateelectrode 5 and right below the epitaxial layer 9 since the gateelectrode 5 and the epitaxial layer 9 serve as a mask. Therefore, aconcentration of the p-type impurity (for example, B (boron)) in theupper surface of the semiconductor substrate 1 is higher in a regionoutside the gate electrode 5 right below the portion between the gateelectrode 5 and the epitaxial layer 9 than a portion right below thegate electrode 5. Similarly, the concentration of the p-type impurity(for example, B (boron)) in the upper surface of the semiconductorsubstrate 1 is higher in a region right below the portion between thegate electrode 5 and the epitaxial layer 9 than a portion right belowthe epitaxial layer 9.

In this manner, a reason why the halo region 11 is not formed in theportion right below the gate electrode 5 but formed only in the vicinityof the portion right below both ends of the gate electrode 5 is that afilm thickness including those of the gate electrode 5, the gateinsulating film 4, the silicon layer 3, and the BOX film 2 is thickerthan a film thickness including those of the silicon oxide film 7, thesilicon layer 3, and the BOX film 2. Similarly, a reason why the haloregion 11 is not formed in the portion right below the epitaxial layer 9but formed only in the vicinity of the portion right below the both endsof the gate electrode 5 is that the film thickness including those ofthe epitaxial layer 9, the silicon layer 3, and the BOX film 2 isthicker than the film thickness including those of the silicon oxidefilm 7, the silicon layer 3, and the BOX film 2. Note that the filmthickness of the BOX film 2 is about 10 to 50 nm, and is 10 nm here.Also, the film thickness of the silicon layer 3 is about 5 to 15 nm, andis 10 nm here.

Note that, in the present embodiment, the method has been explained, inwhich the ion implantation step of forming the halo region 11 isperformed after the ion implantation step of forming the extensionregion 10. However, the halo region 11 may be formed before theformation of the extension region 10. However, the extension region 10and the halo region 11 are formed always after the formation of theepitaxial layer 9.

Next, as illustrated in FIG. 6, by using, for example, the CVD method, asilicon nitride film 8 b is formed so as to cover the exposed surface ofeach of the gate electrode 5, the silicon oxide film 7, the siliconlayer 3, and the epitaxial layer 9. Then, the silicon nitride film 8 bis partially removed by performing the anisotropic etching by, forexample, the RIE method to expose the upper surface of each of the gateelectrode 5, the silicon layer 3, and the epitaxial layer 9. In thismanner, the silicon nitride film 8 b is formed on the side wall of thegate electrode 5 via the silicon oxide film 7 in the self alignment. Inthis manner, a side wall formed of the silicon oxide film 7 and thesilicon nitride film 8 b is formed on the side wall of the gateelectrode 5.

Next, as illustrated in FIG. 7, an n-type impurity (for example, As(arsenic)) is ion-implanted from above the semiconductor substrate 1 ata relatively high concentration with using the gate electrode 5, thesilicon oxide film 7, and the silicon nitride film 8 b as a mask, sothat a diffusion layer 12 is formed inside the epitaxial layer 9 exposedfrom the gate electrode 5, the silicon oxide film 7, and the siliconnitride film 8 b. The diffusion layer and the epitaxial layer 9 aresemiconductor regions which configure source/drain regions. Theabove-described source/drain regions have a LDD (Lightly Doped Drain)structure having the extension region 10 containing thelow-concentration impurity between the diffusion layer 12 to which theimpurity has been introduced at the high concentration and the siliconlayer 3 to be a channel region right below the gate electrode 5.Therefore, an impurity concentration of the diffusion layer 12 is higherthan an impurity concentration of the extension region 10.

Through the above-described process, an n-channel-type MOSFET Qaincluding the gate electrode 5, the extension region 10, and thediffusion layer 12 is formed. Although detailed explanations andillustration of steps subsequent to this are omitted, the semiconductordevice of the present embodiment is completed by forming a silicidelayer on the gate electrode 5 and the diffusion layer 12, and then,covering the MOSFET Qa with an interlayer insulating film, connecting acontact plug which penetrates through the interlayer insulating film tothe silicide layer, and forming a wiring connected to the contact plugand the upper surface of the gate electrode 5.

In the upper surface of the semiconductor substrate 1 illustrated inFIG. 7, it is assumed that a region right below the gate electrode is afirst region, that a region right below the extension region 10 is asecond region, and that a region right below the diffusion layer 12 is athird region. The first region, the second region, and the third regionare arranged to be align in one direction in the upper surface of thesemiconductor substrate 1, the first region is arranged so as to besandwiched by the second regions, and the first region and the secondregions are arranged so as to be sandwiched by the third regions. Sincethe halo region 11 which is an impurity diffusion layer is formed in thesecond region, the concentration of the impurity introduced into thehalo region 11 is higher in the second region than the first region, andis higher in the second region than the third region.

Next, effects of the semiconductor device of the present embodiment andthe method of manufacturing thereof will be explained by usingcomparative examples of FIGS. 18 to 20. FIGS. 18 and 19 arecross-sectional views during manufacturing steps of a semiconductordevice including a MOSFET as a comparative example, and FIG. 20 is across-sectional view of a semiconductor device including a MOSFET Qd asa comparative example.

The following step is conceivable (see FIG. 18) as one of steps offorming a MOSFET on a SOI substrate including the semiconductorsubstrate 1, the BOX film 2, and the silicon layer 3. That is, first,the gate electrode 5 is formed on the silicon layer 3, and then, theextension region 10 a is formed in the upper surface of the siliconlayer 3 by performing the ion implantation, and then, the side wallformed of the silicon oxide film 7 and the silicon nitride (Si₃N₄) film8 is formed on the side wall of the gate electrode 5 in the selfalignment.

In a subsequent step, for the above-described reasons, an epitaxiallayer is formed outside the gate electrode 5 and the side wall by theepitaxial growth method in order to compensate for the film thickness ofthe silicon layer.

However, if the extension region 10 a is formed before the formation ofthe epitaxial layer, there is a risk that epitaxial layers 9 a, 9 b, and9 c are not formed to have desired film thicknesses and shapes asillustrated in FIG. 19. That is, as the epitaxial layers 9 a and 9 billustrated in FIG. 19, it is conceivable that the epitaxial layers arenot uniformly grown on the silicon layer 3 and have variation incrystalline characteristics. Also, as the epitaxial layer 9 c, it isconceivable that the epitaxial layer is hardly grown and the layerincluding the silicon layer 3 and the epitaxial layer 9 c cannot obtaina desired film thickness. If the epitaxial layer 9 is excessively thin,there is a risk that the film thickness of the silicon layer includingthe epitaxial layer 9 is insufficient when the silicide layer is formedon the epitaxial layer 9, and all of the source/drain regions arechanged to be silicide.

A reason why the epitaxial layer is not formed in the desired shape asdescribed above is that, when the epitaxial layer is formed on thesilicon layer 3 which has been damaged by the ion implantation step forforming the extension region 10 a, the epitaxial layer is not grown welldue to the damage. If the epitaxial layer is not normally formed, thereis a problem that the silicide layer is not formed well and theshort-channel characteristics are deteriorated.

On the other hand, as explained with reference to FIGS. 1 to 7, theepitaxial layer 9 can be formed so as to have the desired shape and filmthickness on the silicon layer 3 which has not been damaged by the ionimplantation for forming the extension region by forming the siliconoxide film 7 and the silicon nitride film 8 a on the side wall of thegate electrode 5 before the formation of the epitaxial layer 9, andthen, forming the epitaxial layer in that state. Even in a stepsubsequent to the formation of the epitaxial layer 9, the extensionregion 10 can be formed in the upper surface of the silicon layer 3 byperforming the ion implantation after the silicon nitride film 8 a isremoved.

Here, in the present embodiment, as explained with reference to FIG. 5,the halo region 11 is formed in the upper surface of the semiconductorsubstrate 1. As a method of forming the halo region in the upper surfaceof the semiconductor substrate, as the semiconductor device illustratedin FIG. 20 as the comparative example, it is conceivable to form a haloregion (p-type semiconductor region) 11 a in the entire upper surface ofthe semiconductor substrate 1 from above the SOI substrate before theformation of the gate electrode 5 and others, and then, form the gateelectrode 5, the extension region 10 a, a side wall, an epitaxial layer,and a diffusion layer 12 a.

When the halo region is formed in the principal surface of thesemiconductor substrate 1, the short-channel characteristics can besuppressed. The short-channel characteristics described here includesdeterioration of Lg-Vth characteristics, deterioration of DIBL (DrainInduced Barrier Lowering), and deterioration of an S value(sub-threshold coefficient: sub-threshold slope).

The Lg-Vth characteristics are characteristics determined by a relationbetween a gate length Lg of the gate electrode and a threshold voltageVth. When the MOSFET is miniaturized, there is a tendency that an amountof change in the Vth increases depending on a used gate length, andtherefore, a problem that the threshold voltage Vth is tend to be variedamong MOSFETs arises due to fine variation in the gate length, andreliability of the semiconductor device is deteriorated.

Also, the DIBL is characteristics that change in the threshold voltageVth increases when a drain voltage of the miniaturized MOSFET increases,and refers to a barrier lowering effect caused by increase in theinfluence of the drain voltage. If the characteristics are deteriorateddue to the channel shortening, the threshold voltage Vth decreases asthe drain voltage increases, and a depletion layer of the drain regionis extended, and therefore, leakage current between the source/drainregions increases.

Further, the S value represents inverse of a slope of a graph obtainedwhen a relation between the gate voltage Vg and a drain current Id isgraphed. When the S value is increased by the channel shortening, risingof a current is gradual, and therefore, a problem of decrease in acurrent drive force of the MOSFET arises. Still further, when the Svalue is large, the leakage current in an off state of the MOSFETincreases even if the threshold voltage Vth is the same.

These above-described problems of the short-channel characteristics canbe improved by forming the halo region in the principal surface of thesemiconductor substrate 1. When the halo region is formed in the uppersurface of the semiconductor substrate which is the supporting substrateof the SOI substrate, the effect of suppressing the short-channelcharacteristics particularly described above can be achieved. On theother hand, when the halo region is formed in the deep region away fromthe upper surface of the semiconductor substrate, the effect ofsuppressing the short-channel characteristics becomes small.

Still further, as illustrated in the comparative example of FIG. 20, ina case that the halo region 11 a is formed in a portion in the uppersurface of the semiconductor substrate 1 right below the gate electrode5 and a case that the halo region is formed in other portion than theportion therein right below the gate electrode 5, the short-channelcharacteristics can be more effectively suppressed in the case that thehalo region is formed in other portion in the upper surface of thesemiconductor substrate than the portion right below the gate electrode5.

In the semiconductor device of the present embodiment, as explained withreference to FIG. 5, the halo region 11 is formed by performing the ionimplantation with using the gate electrode 5 and the epitaxial layer 9as the mask, and the halo region is not formed in the portion rightbelow the gate electrode 5, and therefore, the short-channelcharacteristics can be more effectively suppressed. That is, in theupper surface of the semiconductor substrate 1, the concentration of theimpurity that configures the halo region is higher in a region rightbelow the portion between the gate electrode and the epitaxial layer 9than the portion right below the gate electrode 5, and therefore, theshort-channel characteristics can be more effectively suppressed.

Still further, as illustrated in the comparative example of FIG. 20,when the halo region 11 a is formed in the entire upper surface of thesemiconductor substrate 1, the halo region 11 a to which the impurityhas been introduced at the high concentration is formed right below thediffusion layer 12 a to which the impurity has been introduced at thehigh concentration via the BOX film 2. In this case, a diffusioncapacitance (parasitic capacitance, junction capacitance) is generatedbetween the diffusion layer 12 a and the halo region 11 a. Therefore,particularly in a MOSFET having a high operating frequency, signalnoise, delay, or others is significantly generated.

As one structure for preventing the generation of the capacitance, astructure is conceivable, in which the halo region is not formed rightbelow the diffusion layer 12 which configures the source/drain regions.In the present embodiment, as explained with reference to FIG. 5, thehalo region 11 is formed by performing the ion implantation with usingthe gate electrode 5 and the epitaxial layer 9 as the mask, and the haloregion is not formed right below the epitaxial layer 9. Therefore, thegeneration of the diffusion capacitance between the diffusion layer 12and the semiconductor substrate 1 can be prevented.

Note that, if ion implantation which forms the halo region in the entireupper surface of the semiconductor substrate is performed from the uppersurface of the SOI substrate before the formation of the gate electrode,the side wall, and others, the problems that the short-channelcharacteristics and the diffusion capacitance occur arise as describedabove. On the other hand, if the halo region is not formed in the entireupper surface of the semiconductor substrate but formed in only apredetermined region inside the semiconductor substrate by performingthe ion implantation with using a photoresist film or others as a mask,the occurrence of the above-described problems can be avoided. However,when this method is used, it is required to prepare the mask used in theion implantation step of forming the halo region and to increase a stepof forming the photoresist film, and therefore, a manufacturing cost ofthe semiconductor device is increased.

In the present embodiment, the ion implantation of forming the haloregion is performed with using the gate electrode illustrated in FIG. 5and the epitaxial layer 9 which has been formed in the self alignment asthe mask, and therefore, it is not required to newly prepare the mask,and the manufacturing steps of the semiconductor device can besimplified, and the increase in the manufacturing cost of thesemiconductor device can be prevented.

Second Embodiment

In the above-described first embodiment, the method of forming theMOSFET by a gate first process in which the source/drain regions areformed after the gate electrode is formed has been explained. In thepresent embodiment, a MOSFET formed by a gate last process, in which thegate electrode is formed after the source/drain regions are formed willbe explained.

Hereinafter, FIGS. 8 to 12 illustrate cross-sectional views duringmanufacturing steps of a semiconductor device of the present embodiment.

First, as similarly to the above-described first embodiment, the SOIsubstrate including the semiconductor substrate 1, the BOX film 2 formedon the semiconductor substrate 1, and the silicon layer 3 formed on theBOX film 2 is prepared. Then, steps almost similar to the stepsexplained with reference to FIGS. 1 and 2 are performed.

Note that, in the steps explained with reference to FIGS. 1 and 2, thegate electrode 5 formed of the polysilicon film is formed. However,here, instead of the gate electrode 5, for example, a dummy gateelectrode (sacrifice pattern) D5 formed of a polysilicon film is formed.A material and a pattern shape of the dummy gate electrode D5 are thesame as those of the gate electrode 5 of the above-described embodiment.Also, the gate insulating film 4 (see FIG. 1) is not formed. Further,the implantation of the impurity for forming the extension region 10 isperformed after the formation of the dummy gate electrode D5 but beforethe formation of the side wall formed of the silicon oxide film 7 andthe silicon nitride film 8 a. In this manner, the extension region 10 towhich an n-type impurity (for example, As (arsenic)) is implanted at arelatively low concentration is formed in the upper surface of thesilicon layer 3 on both sides of the dummy gate electrode D5.

That is, here, after a pattern formed of a stacked film formed of thedummy gate electrode D5 and the silicon nitride film 6 is formed on theSOI substrate, and then, the extension region 10 is formed, and asidewall formed of the silicon oxide film 7 and the silicon nitride film8 a is subsequently formed on a side wall of the dummy gate electrodeD5. Subsequently, the epitaxial layer 9 is formed on the silicon layer 3that is exposed from the side wall and the dummy gate electrode D5.

Then, an n-type impurity (for example, As (arsenic)) is ion-implantedinto the epitaxial layer 9 at a relatively high concentration, so thatthe diffusion layer 12 is formed inside the epitaxial layer 9 that isexposed from the dummy gate electrode D5, the silicon oxide film 7 andthe silicon nitride film 8 a. In this manner, a structure illustrated inFIG. 8 is obtained. The extension region 10 and the diffusion layer 12configure source/drain regions of a MOSFET Qb (see FIG. 12) which willbe formed later.

Next, as illustrated in FIG. 9, a silicide layer 13 is formed on thesurface of the diffusion layer 12 by using an already-known salicidetechnique. The silicide layer 13 is a conductive film made of cobaltsilicide (CoSi). At this time, an upper surface of the dummy gateelectrode D5 is covered with the silicon nitride film 6, and therefore,the silicide layer is not formed on the upper surface of the dummy gateelectrode D5.

Then, an etching stopper film (liner insulating film) 14 and aninterlayer insulating film 15 are sequentially formed so as to cover thesilicon layer 3, the silicide layer 13, the side wall, the siliconnitride film 6, and the source/drain regions by using, for example, theCVD method. The etching stopper film 14 is a film which functions as anetching stopper film in an etching step of forming a contact hole forburying a contact plug to be electrically connected to the diffusionlayer 12 in a later step, and is formed of, for example, a siliconnitride (Si₃N₄) film. Also, the interlayer insulating film 15 is formedof, for example, a silicon oxide film, and an upper surface thereof ispositioned in a region higher than at least the upper surface of thedummy gate electrode D5.

Subsequently, the interlayer insulating film 15, the etching stopperfilm 14, and the silicon nitride film 6 are polished by using a CMP(Chemical Mechanical Polishing) method, so that the upper surface of thedummy gate electrode D5 is exposed, and upper-surface heights of thedummy gate electrode D5, the etching stopper film 14, and the interlayerinsulating film 15 are uniformed.

Next, as illustrated in FIG. 10, the dummy gate electrode D5 isselectively removed by using, for example, a wet etching method. In thismanner, an opening portion OP1 of an insulating film is formed in aregion from which the dummy gate electrode D5 has been removed, so thatthe upper surface of the silicon layer 3 is exposed from a bottomsurface of the opening portion OP1. The opening portion OP1 describedhere is an opening portion of the insulating film formed of the etchingstopper film 14, the interlayer insulating film 15, the silicon oxidefilm 7, and the silicon nitride film 8 a, and a side wall of the siliconoxide film 7 is exposed from a side wall of the opening portion OP1.

Next, as illustrated in FIG. 11, an impurity (for example, B (boron) orP (phosphorous)) is ion-implanted into the principal surface of thesemiconductor substrate 1, so that a halo region 16 obtained byimplanting the impurity into the upper surface of the semiconductorsubstrate 1 is formed. Here, the above-described ion implantation isperformed in a direction perpendicular to the principal surface of thesemiconductor substrate 1, so that the impurity is implanted into theprincipal surface of the semiconductor substrate 1 so as to pass throughthe silicon layer 3 at the bottom surface of the opening portion OP1 andthrough the BOX film 2 therebelow.

At this time, the semiconductor substrate 1 and the silicon layer 3 inother region than the opening portion OP1 from which the dummy gateelectrode D5 has been removed are covered with the interlayer insulatingfilm 15, the etching stopper film 14, the silicide layer 13, the siliconoxide film 7, and the silicon nitride film 8 a, and therefore, theimpurity is not implanted into the semiconductor substrate 1 and thesilicon layer 3 in this region. Also, the diffusion layer 12 is coveredwith the interlayer insulating film 15, the etching stopper film 14, andthe silicide layer 13, and therefore, the impurity is not implantedthereto.

Next, as illustrated in FIG. 12, a gate insulating film 17 and a gateelectrode 18 are formed so as to be buried inside the opening portionOP1. In this case, first, a high dielectric-constant insulating film isformed on the entire upper surface of the semiconductor substrate 1 soas to cover the bottom surface of the opening portion OP1 and an innerwall thereof by using, for example, an ALD (Atomic Layer Deposition)method or the CVD method. Subsequently, a metal film is formed so as tocompletely bury the inside of the opening portion OP1 by using asputtering method or others. The above-described metal film is formedof, for example, a TiN film.

The high dielectric-constant insulating film is an insulating filmcontaining Hf, is made of an insulating material containing Hf(hafnium), and can be, for example, a. HfSiON film (hafnium siliconoxynitride film), a HfON film (hafnium oxynitride film), or a HfO film(hafnium oxide film, typically, HfO₂ film). When the highdielectric-constant film is the HfSiON film, a HfSiO film is depositedfirst by using the ALD (Atomic Layer Deposition) method or the CVDmethod. Then, this HfSiO film is nitrided by a nitriding process, sothat the HfSiON film can be formed.

Next, an unnecessary part of the above-described metal film on theinterlayer insulating film and an unnecessary part of theabove-described high dielectric-constant insulating film are removed bypolishing them by using the CMP method, so that the upper surface of theinterlayer insulating film 15 is exposed. In this manner, theabove-described metal film and the above-described highdielectric-constant insulating film are buried so as to remain onlyinside the opening portion OP1, and a gate insulating film 17 formed ofthe above-described high dielectric-constant insulating film and a gateelectrode 18 formed of the above-described metal film are formed. Thatis, by the above-described polishing step, upper-surface heights of thegate electrode 18 and the interlayer insulating film 15 are uniformed.At this time, between the side walls of the interlayer insulating film15 which are opposed to each other so as to sandwich the opening portionOP1, the etching stopper film 14, the silicon nitride film 8 a, thesilicon oxide film 7, the gate insulating film 17, and the gateelectrode 18 are sequentially formed in this order from each of the bothside walls of the interlayer insulating film 15.

The gate insulating film 17 is continuously formed inside the openingportion OP1 so as to be along the upper surface of the silicon layer 3and the side wall of the silicon oxide film 7. Therefore, the gateinsulating film 17 is formed between the silicon layer 3 and the gateelectrode 18, and the gate insulating film 17 covering the side wall ofthe gate electrode 18 is formed between the silicon oxide film 7 and thegate electrode 18. Therefore, the gate electrode 18, the silicon layer3, and the silicon oxide film 7 are not in contact with each other, andare electrically insulated from each other. In this manner, then-channel-type MOSFET Qb including the gate electrode 18, the extensionregion 10, and the diffusion layer 12 is formed.

Detailed explanations and illustrations of subsequent steps will beomitted. However, an interlayer insulating film is further formed on theinterlayer insulating film 15 and on the gate electrode 18, and then, acontact plug penetrating through this interlayer insulating film and theinterlayer insulating film 15 is formed, and the contact plug isconnected to the silicide layer 13 and the gate electrode 18.Subsequently, a wiring connected to an upper surface of theabove-described contact plug is formed, so that the semiconductor deviceof the present embodiment is completed. Note that the step of formingthe silicide layer on the upper surface of the gate electrode 18 is notrequired.

Through the ion implantation step explained with reference to FIG. 11,the MOSFET Qb formed by the above-described manufacturing steps has thehalo region 16 in a portion of the upper surface of the semiconductorsubstrate 1 which is right below the opening portion OP1, that is, rightbelow the gate electrode 18 illustrated in FIG. 12. The halo region 16is not formed in a region of the principal surface of the semiconductorsubstrate 1 which is covered with the etching stopper film 14, theinterlayer insulating film 15, the silicon oxide film 7, and the siliconnitride film 8 a.

This is because the impurity for configuring the halo region 16 is notimplanted into the region of the semiconductor region 1 which is coveredwith the etching stopper film 14 and the interlayer insulating film 15through the ion implantation step explained with reference to FIG. 11.Therefore, the halo region 16 is not formed in the portion of theprincipal surface of the semiconductor substrate 1 which is right belowthe diffusion layer 12 formed beside the gate electrode 18 illustratedin FIG. 12.

That is, in a first region of the upper surface of the semiconductorsubstrate 1 which is right below the gate electrode 18, a concentrationof the n-type or the p-type impurity which has been implanted in the ionimplantation step explained with reference to FIG. 11 is higher than ina second region adjacent to the first region in the upper surface of thesemiconductor substrate 1. Note that the first region and the secondregion described here are arranged to be align in a gate-lengthdirection (first direction) of the gate electrode 18 as similar to theextension region 10, the diffusion layer 12, and the gate electrode 18.Here, although the gate electrode 18 is not formed right above thesecond region, the source/drain regions are formed right above thesecond region.

As described above, the halo region 16 is a semiconductor region formedfor adjusting and improving the Lg-Vth characteristics of the MOSFET Qb.That is, the formation of the halo region 16 can prevent the occurrenceof the phenomenon caused due to the channel shortening which decreasesthe threshold voltage Vth when the drain voltage increases, resulting inthe extension of the depletion layer of the drain region to increase theleakage current between the source/drain regions.

As the method of forming the halo region in the upper surface of thesemiconductor substrate, the following method is conceivable. That is,as similar to the semiconductor device illustrated as the comparativeexample in FIG. 20, it is conceivable to form a halo region 11 a byperforming ion implantation into the entire upper surface of thesemiconductor substrate 1 from above the SOI substrate before theformation of the gate electrode 5, the diffusion layer 12 a, and others,and then, form the gate electrode 5, the extension region 10 a, the sidewall, the epitaxial layer, the diffusion layer 12 a, and others.

Also, when the gate last process is used as similar to the presentembodiment, it is conceivable to form the halo region (not illustrated)in the entire principal surface of the semiconductor substrate 1 byperforming the ion implantation into the semiconductor substrate 1 afterthe preparation of the SOI substrate but before the formation of thedummy gate electrode D5, the epitaxial layer 9, and the diffusion layer12 (see FIG. 8). In this case, the halo region is formed, via the BOXfilm 2, right below the region to which the n-type impurity (forexample, As (arsenic)) has been introduced at the high concentration assimilar to the diffusion layer 12 (see FIG. 8).

When the halo region is formed in the entire principal surface of thesemiconductor substrate 1 as described above, a diffusion capacitance(parasitic capacitance, junction capacitance) is generated between thediffusion layer 12 and the halo region formed via the BOX film 2therebetween, and therefore, signal noise or delay is generated when theMOSFET is operated.

On the other hand, in the semiconductor device of the presentembodiment, through the step of forming the MOSFET Qb by using the gatelast process, the halo region 16 is formed in only the portion of theupper surface of the semiconductor substrate 1 which is right below theopening portion OP1 by performing the ion implantation into the openingportion OP1 (see FIG. 1) where the dummy gate electrode D5 has beenremoved. Therefore, the halo region 16 is not formed in the portion ofthe upper surface of the semiconductor substrate 1 which is right belowthe diffusion layer 12. In this manner, the provision of the halo regioncan suppress the short-channel effect and obtain the effect capable ofadjusting the threshold voltage Vth, and besides, can prevent theoccurrence of of the diffusion capacitance between the diffusion layer12 and the semiconductor substrate 1.

Also, in the present embodiment, the halo region is not formed in onlythe portions of the principal surface of the semiconductor substrate 1which are below the both side walls (both ends) of the gate electrode18, but the halo region 16 is formed in the portion of the entireprincipal surface of the semiconductor substrate 1 which is right belowthe gate electrode 18. In the case that the halo region 16 is formed inthe portion of the entire principal surface of the semiconductorsubstrate 1 which is right below the gate electrode 18 as describedabove, the impurity for configuring the halo region 16 is uniformlydistributed below the gate electrode 18, and therefore, the variation inthe threshold voltage can be suppressed and the deterioration of theDIBL can be prevented further than those in the case that the haloregion is formed in only the portions of the principal surface of thesemiconductor substrate 1 which are below the both side walls (bothends) of the gate electrode 18.

Third Embodiment

In the present embodiment, the case that the MOSFET is formed by thegate last process as similar to the above-described second embodimentwill be explained. Hereinafter, a step of manufacturing a semiconductordevice of the present embodiment, which form a halo region in onlyportions which are right below both ends of a gate electrode byperforming ion implantation into a region from which an offset spacerhas been removed will be explained with reference to FIGS. 13 to 17.FIGS. 13 to 17 are cross-sectional views for explaining the step ofmanufacturing the semiconductor device of the present embodiment.

First, as illustrated in FIG. 13, the SOI substrate including thesemiconductor substrate 1, the BOX film 2, and the silicon layer 3 isprepared as similar to those of the above-described first and secondembodiments. Subsequently, a polysilicon film and the silicon nitridefilm 6 (not illustrated) are formed on the silicon layer 3 by the CVDmethod or others, and then, the silicon nitride film 6 (not illustrated)is patterned, and the polysilicon film is processed with using thepatterned silicon nitride film 6 (not illustrated) as a hard mask, sothat the dummy gate electrode (sacrifice pattern) D5 is formed of thepolysilicon film.

Subsequently, an insulating film is formed on the silicon layer 3 so asto cover an upper surface of the dummy gate electrode D5 and a sidesurface thereof by using the CVD method or others. Then, by performinganisotropic etching, the upper surface of the dummy gate electrode D5and the upper surface of the silicon layer 3 are exposed, and an offsetspacer OSS formed of an insulating film is formed on the side wall ofthe dummy gate electrode D5 in self alignment. As a material of theoffset spacer, for example, silicon germanium (SiGe), titanium nitride(TiN), or others can be used.

Subsequently, for example, a side wall SW including a silicon oxide filmis formed on the side wall of the offset spacer OSS. The side wall SWcan be formed by, for example, forming a stacked film formed of asilicon oxide film and a silicon nitride film on the entire uppersurface of the semiconductor substrate 1 by the CVD method or others,and then, partially removing the stacked film by anisotropic etching.Subsequently, the epitaxial layer 9 is formed by an epitaxial growthmethod on the upper surface of the silicon layer 3 exposed from thedummy gate electrode D5, the offset spacer OSS, and the side wall SW. Atthis time, the epitaxial layer is not formed on an upper surface of thedummy gate electrode D5 since the upper surface of the dummy gateelectrode D5 is covered with the silicon nitride film 6 (notillustrated). Subsequently, an n-type impurity (for example, As(arsenic)) is ion-implanted into the epitaxial layer 9 at a relativelyhigh concentration, so that the diffusion layer 12 which is the n-typesemiconductor layer is formed inside the epitaxial layer 9.

Subsequently, as similar to the step explained in the above-describedsecond embodiment with reference to FIG. 9, the silicide layer 13, theetching stopper film 14, and the interlayer insulating film 15 areformed, and a part of the etching stopper film 14 and the interlayerinsulating film 15 and the silicon nitride film 6 (not illustrated) areremoved by a polishing step with using, for example, the CMP method, sothat an upper surface of the dummy gate electrode D5 and an uppersurface of the offset spacer OSS are removed.

That is, the silicide layer 13 is formed on the surface of the diffusionlayer 12 by using the publicly-known salicide technique, and then, theetching stopper film 14 and the interlayer insulating film 15 aresequentially formed by using the CVD method or others so as to cover thediffusion layer 12, the silicide layer 13, the side wall SW, the offsetspacer OSS, and the silicon nitride film 6 (not illustrated). Then, theetching stopper film 14, a part of the interlayer insulating film 15,and the silicon nitride film (not illustrated) are polished by using,for example, the CMP method, so that upper-surface heights of theinterlayer insulating film 15, the dummy gate electrode D5, and theoffset spacer OSS are uniformed.

Next, as illustrated in FIG. 14, the offset spacer OSS is selectivelyremoved by the wet etching method or others, so that the upper surfaceof the silicon layer 3 beside the dummy gate electrode D5 is exposed.When the offset spacer OSS is formed of the titanium nitride (TiN) film,the offset spacer OSS is removed by using, for example, a SPM (sulfuricacid hydrogen peroxide mixture) solution which is mixed liquid ofconcentrated sulfuric acid and hydrogen peroxide. In this manner, anopening portion OP2 is formed in a region from which the offset spacerOSS is removed. Inside the opening portion OP2, both side walls of thedummy gate electrode D5 and a side wall of the side wall SW are exposed.That is, the opening portion OP2 is formed between the dummy gateelectrode D5 and the side wall SW, the etching stopper film 14, and theinterlayer insulating film 15.

Next, as illustrated in FIG. 15, an impurity (for example, B (boron) orP (phosphorous)) is ion-implanted toward the principal surface of thesemiconductor substrate 1, so that a halo region 19 obtained byimplanting the above-described impurity into the upper surface of thesemiconductor substrate 1 is formed. Here, the above-described ionimplantation is performed from the direction perpendicular to theprincipal surface of the semiconductor substrate 1, and theabove-described impurity is implanted into the principal surface of thesemiconductor substrate 1 so as to pass through the silicon layer 3 atthe bottom surface of the opening portion OP2 and the BOX film 2therebelow. In this manner, the halo region 19 is formed in only aregion of the principal surface of the semiconductor substrate 1 whichis right below the opening portion OP2.

That is, the above-described ion implantation is performed with usingthe dummy gate electrode D5, the etching stopper film 14, and theinterlayer insulating film 15 as a mask, and therefore, the halo region19 is not formed in the entire upper surface of the semiconductorsubstrate 1 but formed in only the portion of the principal surface ofthe semiconductor substrate 1 which is beside and right below the dummygate electrode D5. Therefore, in the portions of the principal surfaceof the semiconductor substrate 1 which are right below the dummy gateelectrode D5 and right below the diffusion layer 12, there are regionsto which the impurity for configuring the halo region 19 has not beenintroduced.

Next, as illustrated in FIG. 16, an n-type impurity (for example, As(arsenic)) is ion-implanted toward the upper surface of the siliconlayer 3, so that the extension region 10 a to which the above-describedimpurity has been implanted is formed in the silicon layer 3. Theextension region 10 a is formed right below the opening portion OP2, andthere is a region right below the dummy gate electrode D5 where theextension region 10 a is not formed. That is, the extension region 10 ais formed in only a portion of the silicon layer 3 which is beside thedummy gate electrode D5. In this manner, beside the dummy gate electrodeD5, the source/drain regions having a LDD structure including theextension region 10 a having the relatively low impurity concentrationand the diffusion layer 12 having the relatively high impurityconcentration are formed.

Note that either of the step of forming the halo region 19 explainedwith reference to FIG. 15 and the step of forming the extension region10 a explained with reference to FIG. 16 may be performed first. Also,the step of forming the extension region 10 a by performing the ionimplantation from the opening portion OP2 has been explained here.However, as similar to the above-described second embodiment, theextension region 10 a may be formed inside the silicon layer byperforming the ion implantation at a stage after the formation of thedummy gate electrode but before the formation of the side wall. In thatcase, the ion implantation explained with reference to FIG. 16 is notperformed.

Next, by performing the steps explained with reference to FIGS. 10 and12, a MOSFET Qc illustrated in FIG. 17 is formed. That is, the dummygate electrode D5 is removed, and then, the gate insulating film 17 andthe gate electrode 18 are formed without performing the ion implantationstep as explained with reference to FIG. 11.

More specifically, after the opening portion OP1 is formed by removingthe dummy gate electrode D5, and a high dielectric-constant insulatingfilm and a metal film are sequentially formed on the entire principalsurface of the semiconductor substrate 1, and then, the highdielectric-constant insulating film and the metal film are polished bythe CMP method or others so as to expose the upper surface of theinterlayer insulating film 15. That is, the gate insulating film 17formed of the high dielectric-constant insulating film is formed so asto cover the side wall and the bottom surface inside the opening portionOP1, and the gate electrode 18 formed of the metal film is formed so asto completely bury the inside of the opening portion OP1 together withthe gate insulating film 17. In this manner, the n-channel-type MOSFETQc including the gate electrode 18, the extension region 10 a, and thediffusion layer 12 is formed.

Detailed explanations and illustrations of subsequent steps will beomitted. However, after an interlayer insulating film is further formedon the interlayer insulating film 15 and the gate electrode 18, andthen, a contact plug penetrating through this interlayer insulating filmand the interlayer insulating film 15 is formed, and the contact plug isconnected to the silicide layer 13 and the gate electrode 18.Subsequently, a wiring connected to an upper surface of the contact plugis formed, so that the semiconductor device of the present embodiment iscompleted. Note that the step of forming the silicide layer on the uppersurface of the gate electrode 18 is not required.

Although the semiconductor device of the present embodiment has astructure almost the same as that of the semiconductor device explainedin the above-described second embodiment, this is different from that ofthe above-described second embodiment in the point that the portion ofthe principal surface of the semiconductor substrate 1 which is rightbelow the gate electrode 18 has a region where the halo region 19 is notformed. That is, in the MOSFET Qc in the semiconductor device of thepresent embodiment, as different from the above-described secondembodiment, the halo region 19 is formed in only the portion of theprincipal surface of the semiconductor substrate 1 which is below theboth side walls (both ends) of the gate electrode 18.

In other words, the halo region 19 is formed in only a second region inthe present embodiment when it is assumed that the portion of the uppersurface of the semiconductor substrate 1 which is right below the gateelectrode 18 is a first region, that the upper surface of thesemiconductor substrate 1 includes the second region adjacent to thefirst region in a gate-length direction (first direction) of the gateelectrode 18, and that the upper surface of the semiconductor substrate1 includes third regions so as to sandwich the first region and thesecond region in the same direction. That is, a portion of the uppersurface of the semiconductor substrate 1 which is right below the offsetspacer OSS (see FIG. 13) is the second region, and portions of the uppersurface of the semiconductor substrate 1 which are right below thesource/drain regions are the third regions. In this case, theconcentration of the n-type or p-type impurity implanted in the ionimplantation step explained with reference to FIG. 15 is higher in thesecond region than any other regions of the first region and the thirdregion.

As described above, when the halo region 19 is formed in the portion ofthe principal surface of the semiconductor substrate 1 which is rightbelow the diffusion layer 12, there is a problem that the diffusioncapacitance (parasitic capacitance, junction capacitance) between thediffusion layer 12 and the halo region 19 is increased. On the otherhand, in the present embodiment, the halo region 19 is not formed rightbelow the diffusion layer 12, and therefore, occurrence of signal noiseor delay of the MOSFET due to the increase in the diffusion capacitancecan be prevented. Also, the short-channel characteristics can besuppressed by forming the halo region 19 in the principal surface of thesemiconductor substrate 1.

In the foregoing, the invention made by the present inventors has beenconcretely described based on the embodiments. However, it is needlessto say that the present invention is not limited to the foregoingembodiments and various modifications and alterations can be made withinthe scope of the present invention.

For example, in the above-described first to third embodiments, the casethat the n-channel-type MOSFET is formed on the semiconductor substratehas been explained. However, the semiconductor element may be ap-channel-type MOSFET or may be a MIS (Metal Insulator Semiconductor)type FET.

Also, the halo region of the above-described first embodiment has beenexplained as the p-type semiconductor region. However, the conductivitytypes of the halo regions of the above-described first to thirdembodiments may be the same conductivity type as that of a channel ofthe MOSFET thereon or a different conductivity type therefrom.

In addition, a part of the contents described in the embodiments will bedescribed below.

(1) A method of manufacturing a semiconductor device including:

(a) a step of preparing a semiconductor substrate formed of a supportingsubstrate, a first insulating film formed on the supporting substrate,and a semiconductor layer formed on the first insulating film, thesupporting substrate having a first region and a second region adjacentto each other in a first direction in an upper surface thereof;(b) a step of forming a first film on the semiconductor layer;(c) a step of forming a sacrifice pattern formed of the first film rightabove the first region by processing the first film;(d) a step of forming an epitaxial layer on a portion of thesemiconductor layer which is exposed from the sacrifice pattern;(e) a step of forming a pair of source/drain regions sandwiching thesacrifice pattern therebetween in the first direction by introducing animpurity of a first conductivity type into the epitaxial layer;(f) a step of forming a second insulating film on the semiconductorlayer so as to cover the source/drain regions and the semiconductorlayer;(g) a step of forming an opening portion, which exposes an upper surfaceof the semiconductor layer, in the second insulating film by partiallyremoving an upper surface of the second insulating film and removing theexposed sacrifice pattern;(h) after the step of (g), a step of forming a first diffusion layer byintroducing an impurity of the first conductivity type or a secondconductivity type into the first region right below the opening portionfrom above the supporting substrate; and(i) after the step of (h), a step of forming a gate electrode via a gateinsulating film on the semiconductor layer at a bottom portion of theopening portion.(2) In the method of manufacturing the semiconductor device according toitem (1),

the source/drain regions are formed right above the second regions, anda concentration of the impurity of the first conductivity type or thesecond conductivity type introduced into the upper surface of thesupporting substrate is higher in the first region than the secondregions.

(3) A method of manufacturing a semiconductor device including:

(a) a step of preparing a semiconductor substrate formed of a supportingsubstrate, a first insulating film formed on the supporting substrate,and a semiconductor layer formed on the first insulating film, thesupporting substrate having a first region and a second region adjacentto each other in a first direction in an upper surface thereof;(b) a step of forming a first film on a portion of the semiconductorlayer which is right above the first region;(c) a step of forming a sacrifice pattern formed of the first film rightabove the first region by processing the first film;(d) a step of forming a third insulating film which covers a side wallof the sacrifice pattern and is in contact with an upper surface of thesemiconductor layer;(e) a step of forming an epitaxial layer on a portion of thesemiconductor layer which is exposed from the sacrifice pattern and thethird insulating film;(f) a step of forming a pair of source/drain regions sandwiching thesacrifice pattern therebetween in the first direction by introducing animpurity of a first conductivity type into the epitaxial layer;(g) a step of forming a second insulating film on the semiconductorlayer so as to cover the source/drain regions and the semiconductorlayer;(h) a step of forming a first opening portion, which exposes the uppersurface of the semiconductor layer, between the second insulating filmand the sacrifice pattern by partially removing an upper surface of thesecond insulating film and removing the exposed third insulating film;(i) after the step of (h), a step of forming a first diffusion layer byintroducing an impurity of the first conductivity type or a secondconductivity type into the second region right below the first openingportion from above the supporting substrate;(j) after the step of (i), a step of forming a second opening portion,which exposes the upper surface of the semiconductor layer, in thesecond insulating film by removing the sacrifice pattern; and(k) a step of forming a gate electrode via a gate insulating film on thesemiconductor layer at a bottom portion of the second opening portion.(4) In the method of manufacturing the semiconductor device according toitem (3),

a concentration of the impurity of the first conductivity type or thesecond conductivity type introduced into the upper surface of thesupporting substrate is higher in the second region than the firstregion.

(5) In the method of manufacturing the semiconductor device according toitem (3),

the source/drain regions are formed right above third regions formed inthe upper surface of the supporting substrate so as to sandwich thefirst region and the second region therebetween in the first direction,and

a concentration of the impurity of the first conductivity type or thesecond conductivity type introduced into the upper surface of thesupporting substrate is higher in the second region than the thirdregions.

(6) In the method of manufacturing the semiconductor device according toitem (3),

after the step of (h) but before the step of (j), the method includes astep of forming an extension region by introducing an impurity of thefirst conductivity type into the semiconductor layer right below thefirst opening portion from above the supporting substrate at aconcentration lower than that of the epitaxial layer.

What is claimed is:
 1. A method of manufacturing a semiconductor deviceincluding a semiconductor substrate, a first insulating film formed overthe semiconductor substrate and a semiconductor layer formed over thefirst insulating film, comprising steps of: (a) forming a gateinsulating film of a field effect transistor over the semiconductorlayer; (b) forming a gate electrode of the field effect transistor overthe gate insulating film; (c) forming a second insulating film over thesemiconductor layer and a side surface of the gate electrode; (d)providing a first side wall including the second insulating film and athird insulating film by forming the third insulating film over thesemiconductor layer and the side surface of the gate electrode throughthe second insulating film, the third insulating film made of adifferent material from the second insulating film; (e) after the step(d), forming an epitaxial layer over the semiconductor layer and a sideof the first side wall; (f) after the step (e), removing the thirdinsulating film such that the second insulating film located between thesemiconductor layer and the third insulating film is remained; (g) afterthe step (f), forming a first impurity region of a first conductivitytype in the first semiconductor layer through the second insulating filmby an ion implantation method; (h) after the step (g), providing asecond side wall including the second insulating film and a fourthinsulating film by forming the fourth insulating film over thesemiconductor layer and the side surface of the gate electrode throughthe second insulating film, the fourth insulating film made of adifferent material from the second insulating film; and (i) after thestep (h), forming a second impurity region of the first conductivitytype in the epitaxial layer and the first semiconductor layer by an ionimplantation method, wherein the first impurity region is a part of asource region of the field effect transistor or a part of a drain regionof the field effect transistor, and wherein the second impurity regionis a part of the source region of the field effect transistor or a partof the drain region of the field effect transistor, and has largerimpurity concentration than the first impurity region.
 2. A method ofmanufacturing a semiconductor device according to claim 1, furthercomprising a step of: (j) after the step (i), forming silicide layersover the gate electrode and the epitaxial layer.
 3. A method ofmanufacturing a semiconductor device according to claim 1, furthercomprising a step of: (k) between the steps (f) and (h), forming a thirdimpurity region of a second conductivity type being opposite to thefirst conductivity type in the semiconductor substrate by an ionimplantation method.
 4. A method of manufacturing a semiconductor deviceaccording to claim 3, wherein the first conductivity type is an n-type,and wherein the second conductivity type is a p-type.
 5. A method ofmanufacturing a semiconductor device according to claim 1, wherein thesecond insulating film includes a silicon oxide film, and wherein thethird insulating film includes a silicon nitride film.
 6. A method ofmanufacturing a semiconductor device according to claim 1, wherein thesecond insulating film includes a silicon oxide film, and wherein thefourth insulating film includes a silicon nitride film.
 7. A method ofmanufacturing a semiconductor device according to claim 1, wherein thefirst conductivity type is an n-type.